Silent variable delivery hydraulic pump



April 20, 1965 I A. LEHRER SILENT VARIABLE DELIVERY HYDRAULIC PUMP FiledJune 28, 1962 3 Sheets-Sheet 1 FIG.2.

INVENTOR ALEXANDER LEHRER 15. L. ATTORNEY p 20, 1965 A. LEHRER 3,179,060

SILENT VARIABLE DELIVERY HYDRAULIC PUMP Filed June 28, 1962 5Sheets-Sheet 2 FIG .5A. me

as r 12 I02 96 nos I 40 I8 3 2o so 6 6 1 o 3l2 3l6 suo 306 314 INVENTORFIG 3 U ALEXANDER LEHRER TO LOAD BY ATTORNEY United States Patent3,179,060 SILENT VARIABLE DELIVERY HYDRAULIC UMP P Alexander Lehrer,Alexandria, Va., assignor to the United States of America as representedby the Secretary of the The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

This invention relates to hydraulic power transmission systems, and moreparticularly it relates to those systems which function as pumps whendriven mechanically and provide a positive control of fluid flow whenpumping against a pressure head or when pumping in the direction ofpressure drop; the latter being known as overhauling. Machines of thistype are sometimes referred to as servo pumps. The particular machine towhich this invention is specifically directed is the type having arotatable barrel containing a plurality of cylinders and a plurality ofparallel pistons in the cylinders, which pistons move axially along theaxis of rotation of the barrel as the machine is operated.

In hydraulic transmission machines of the type described above, it hasbeen found that considerable noise results during machine operation,especially when such machines are operated under relatively highconditions of load or speed. Such noise may result from the shock whichoccurs when a cylinder having a certain pressure therein is brought intocommunication with a port in a valve plate having a different pressuretherein. In certain environments, such as ships and submarines,hydraulic machines of the type described above have proved to be veryuseful; however, the noise produced by their operation has presented aserious problem. Attempts have been made to reduce or suppress suchnoise by acoustic treatment, flexible mountings, and the like, but suchattempts have not provide entirely satisfactory.

The result is that when quiet operation is a critical factor,

as it is on submarines, such machines cannot be used; and, instead,designers have been forced to employ heavier, less flexible and morecostly fluid transmission devices, such as constant displacement pumps.

An object of this invention is to provide a rotary barrel, parallelpiston machine, of the type described above, wherein the pressuredifference between the cylinders and valve ports is practicallyeliminated, thereby reducing noise generation caused by operation of themachine.

Another object of this invention is to provide a noisefree hydraulicpower transmission system which can be used for bi-directionaloperation.

A further object of this invention is to provide a hydraulic powertransmission machine with a high overall efiiciency, which machine issimple in construction and low in cost of manufacture.

Still another object of this invention is to provide a valve plate foruse with a hydraulic transmission machine of the type described, saidvalve plate including all the valves and passages therein and thus beingeasily adaptable to install on presently existing hydraulic machines inplace of their present valve plates.

Yet another object of this invention is to provide a valve platecontaining all auxiliary ports, valves and passages, thus allowing thecylinder ports to be substantially larger than would be possible if theauxiliary ports, valves and passages were located in the barrel.

3,179,050 Patented Apr. 20, 1965 Further objects and advantages willbecome apparent from the ensuing descriptive matter.

The preferred embodiment of this invention is broadly comprised of avalve means in the form of a plate, and a multi-cylinder, parallelpiston pump. The pump includes a rotatable assembly comprised of abarrel body having a plurality of parallel cylinders therein, each ofsaid cylinders containing a piston. The valve means is located adjacentthe cylinder ports at one end of the barrel body and a swash plate orcam means is located adjacent the barrel body at its other end. As thebarrel body is rotated, the swash plate causes the pistons toreciprocate within the cylinders and thus draw fluid in through thevalve means at one pressure and expel it through the valvemeans atanother pressure.

The valve means is provided with a main suction and a main dischargeport. It is also provided with auxiliary discharge and suction portswhich communicate with the cylinders through check valve equippedpassages and which also communicate with the main ports of the valvemeans through a shuttle valve assembly. The check valve controlledpassages, the auxiliary ports, and the shuttle valve assembly allcooperate so that fluid trapped in each cylinder at suction port closureis either expanded or compressed, as necessary, during its transit ofthe auxiliary ports so that its pressure will be changed to the pressureof the discharge main port. Also residual fluid in each cylinder afterdischarge is also compressed or expanded, as necessary, so that itspressure will be changed to the pressure of the suction main port. Thus,when the fluid is discharged from the cylinder, there is almost nopressure difference and, therefore, substantially no noise caused byshock.

The present invention is a modification of the invention of Francis J.Sisk, disclosed in application Serial No. 200,005 filed June 4, 1962(Navy Case No. 33,256).

The important and advantageous feature of the hydraulic transmissionherein lies in the range'of operation which it is capable of performing.There are two main operational variables to consider. The first variableis directionality; that is, the direction of flow of the fluid throughthe pump (either right to left or left to right). The second variable ispressure conversion; that is, whether the machine converts fluid fromlow pressure to high pressure (pumping) or Whether it converts fluidfrom high pressure to low pressure (overhauling or motoring). Obviously,the interaction of the two variables creates four conditions under whichthe machine must operate; namely:

(1) Pumping right to left (2) Overhauling right to left (3) Pumping leftto right (4) Overhauling left to right The machine of the presentinvention will, depending upon the valve plate used, handle two of theabove conditions or all of them without valving of the main pump flow.

The invention will be more completely understood from the followingdetailed description and claims, read in conjunction with the annexeddrawings, in which:

FIG. 1 is a partial longitudinal section view of an embodiment of amachine in accordance with the present invention;

FIG. 2 is a transverse sectional view taken on a plane indicated by theline 22 of FIG. 1;

FIG. 3 is atransverse sectional view of one embodiment of a valve plateand its associated valve means, showing the shuttle valve in a positionfor pumping from left to right;

FIG. 3A is a partial sectional view showing the shuttle valve of FIG. 3in a position for overhauling or motoring from left to right. In thisembodiment the swash plate operates from zero stroke position to fullstroke in one direction only.

FIG. 4 is a transverse sectional view of another embodiment of the valveplate, shown as part of a schematic illustration of a complete systemcapable of performing under all the operational conditions previouslydiscussed; that is, pumping with or against a pressure differential andpumping in either direction. In this embodiment the swash plate operatesthrough a range from full displacement in one direction through the zeroposition to full displacement in the opposite direction.

Referring now to FIG. 1, a hydraulic power transmission machine or servopump in accordance with the present invention is shown in which a casing16 is closed at one end by a head 12 and at the other end by an annularcover 14 which is attached to the casing by bolts 16. The head 12 isprovided with an inlet passage 18 and and an outlet pasage 20, whichpassages are arranged to communicate with a valve means in the form of astationary circular valve plate 22. A cylindrical shaft 24 is journaledin anti-friction bearings 26 and extends through the valve plate 22 intothe interior of the casing 10. A cylindrical barrel assembly 28 isfixedly mounted on the shaft 24 and adapted to rotate therewith. Thebarrel assembly is spaced from the interior of the casing by means ofroller bearings 30 which allow the barrel assembly to rotate within thecasing.

The cylindrical barrel assembly comprises a cylindrical barrel bodyhaving a plurality of circumferentially spaced cylinders 34 formedtherein, said cylinders being equally radially spaced from and extendingparallel to their axis of rotation which is represented by the shaft 24,as can best be seen in FIG. 2. The cylinder ports or flow slots 36 arelocated adjacent the valve plate 22 and are adapted to effect acommunication, through the valve plate 22, with the inlet passage 18 andthe outlet passage 20.

A piston 42 having a ball head 44 is located within each cylinder and isadapted to reciprocate therein. Each ball head 44 is journalled in anassociated shoe or slipper 48 which rides'freely along the face of aswash plate 48 as the shaft 24 rotates the barrel assembly. The swashplate has a control shaft 56 which controls its angularity. Since theswash plate is disposed angularly or inclined to the axes of thecylinders and pistons, it actually forms a cam surface that causes thepistons 42 to reciprocate as they are being rotated by the barrel 32.

As was aforementioned, the inclination or angularity of the swash plateis controlled by the control shaft 56. When the plane of the swash plateis perpendicular to the axes of the pistons, which is vertical in theembodiment shown in FIG. 1, the stroke of the pistons is zero. As theswash plate is inclined, the stroke of the pistons is increased. Atmaximum inclination of the swash plate, forty-five-degrees displacedfrom the vertical, the stroke of the pistons is at its maximum.

An insert 52 is mounted in the end of shaft 24 and locked to the barrelbody 32, thereby locking the shaft and barrel body together so that theyrotate as a unit. A plunger 54 is mounted in the insert 52 and extendsto the center of the swash plate, with one end of the plunger beingspaced away from the bottom of the insert by compression spring 56 andthe other end of the plunger pressing against a spherical ball 58. Theball 58 freely seats in a seat on the swash plate 48 in such a mannerthat the spherical ball 58 acts as a bearing against which the swashplate bears, so that the swash plate can be rotated through a range ofpositions on opposite sides of' the shaft 24 as indicated by the arrow59 in FIG. 1. The swash plate can be moved to any position within 45degrees on either side of the vertical position, thereby allowingreversible or bi-directional flow. For example, FIG. 1 shows the machineoperating as a pump, with lower pressure fluid being introduced throughinlet 18 {i and as the cylinder assembly 23 is rotated by the shaft 24,the pistons compress the fluid, and the fluid is discharged under highpressure when the associated cylinder communicates with the outlet 20.

The machine of FIG. 1 can also pump in the opposite direction as thatrecited above. That is, lower pressure fluid could be introduced throughthe outlet 20, and as the cylinder assembly is rotated by the shaft 24,the pistons would compress the fluid and discharge it under highpressure when the associated cylinder is in communication with the inlet18. To accomplish this, the swash plate 48 would have to be moved by thecontrol shaft 50 to a position where it was angularly displaced on theother side of the vertical position. An upwardly directed centerline forthe control shaft 50 is shown in FIG. 1 at the upper arrow 59, whichwould correspond to the position of the control shaft under suchreversed conditions.

If it were desired to use the machine only for unidirectional flow, thatis only for pumping and overhauling in one direction the swash platecould be mounted to rotate about a line normal to an axis of one of thepistons, rather than normal to the axis of the centerline of the shaft.An arrangement such as this is shown in United States Patent No.1,506,892. Such an arrangement has the advantages of allowing greatervariations in the length of stroke of the pistons and also of keeping toa minimum the volume in each cylinder at zero stroke, thus keeping to aminimum the amount of energy that can cause noise; however, suchoperation is achieved through the sacrifice of the feature of reversibleor bidirectional fiow. The reversing flow can then be provided by avalve operated with the pump stroke control as shown in FIG. 3.

Referring now to FIG. 3, a valve plate 22 is shown, which plate isadapted for use in the above described machine having the non-reversibletype of swash plate mounting. The valve plate is provided with acircular series of ports which are radially arranged to align with thecylinder slots 36. The ports include two elongated main ports 60 and 62and four auxiliary ports 64, 66, 68 and 76. Each auxiliary port isprovided with a valve controlled passage which connects the auxiliaryport either directly or indirectly to a main port. The indirectconnection is accomplished by connecting the passage to an overhaulingshuttle valve means or assembly 72 which in turn connects to the mainports. A passage or bore 38 connects the main port 60 with the inlet 18and a passage or bore 49 connects the main port 62 with the outlet 2%The auxiliary port 64 is provided with a passage 74 having a one wayvalve 76 therein which allows only inflow to said port. The passage '74connects to a conduit 78 which leads to the shuttle valve assembly '72.The one way valve illustrated is comprised of a spherical ball and acompression spring, but the valve 76 and other similar valves describedherein are not limited to this particular structure. Any one way valvewell known in the art can be used.

The auxiliary port 66 is provided with a passage 80 having a one wayvalve 82 therein which allows only inflow to said port. The passage 80connects to the bore 38. which in turn directly connects to the mainport 60.

The auxiliary port 68 is provided with a passage 84 having a one wayvalve 86 therein which allows only outflow from said port. The passage84 connects to the bore 40 which in turn directly connects to the mainport 62.

The auxiliary port '70 is provided with a passage 88 having a one waycheck valve 90 therein which allows only outflow from said port. Thepassage 88 passes behind bore 40 and connects to a conduit 92 whichleads to the shuttle valve assembly 72..

The shuttle valve means or assembly is comprised of a valve body 94having a plurality of ports therein and a three spool valve member 96adapted to reciprocate selectively in said body to cover or exposecertain of the ports. The conduits 78 and 92 connect to the ports on thelower portion of the valve body 94. A conduit 98, which is connected atone end to the inlet 18 and thus is also connected to the main port 60,is connected at its other end to one of the ports on the upper portionof the valve body 94. The conduit 98 has a branch line 100 which alsoconnects into a port on the upper portion of the valve body, and abranch line 102 which connects into a port at one end of the valve body.A conduit 104, which is connected at one end to the outlet 20 and thusis also connected to the main port 62, is connected at its other end tothe port on the upper portion of the valve body 94 intermediate theports which are connected to conduit 98 and branch line 100. The conduit102 has a branch line 106 which connects into a port at the end of thevalve body opposite to the end where branch line 102 connects.

Movement of the shuttle valve member 96 is controlled exclusively bypressure. When the pressure at main port 62 exceeds the pressure at mainport 60 the valve member 96 shifts to the left, as is shown in FIG. 3,because the pressure flowing into the valve through the line 106 exceedsthe pressure flowing into the valve through the line 102. If thepressure at main port 60 exceeded the pressure at main port 62, thevalve would shift to the position shown in FIG. 3A.

The function of the shuttle valve assembly 72 is merely to alternatelyconnect auxiliary ports 64 and 70 with the main ports. That is, when thevalve member 96 is in the position shown in FIG. 3, the auxiliary port64 is in communication with the main port 60 (through passage 74,conduit 78, line 180, conduit 98 and bore 38) and the auxiliary port 70is in communication with the main port 62 (through passage 88, conduit92, conduit 104 and bore 40).

If the valve member is shifted to the position shown in FIG. 3A, theconnections are reversed so that the auxiliary port 64 is now incommunication with the main port 62 (through passage 74, conduit 78,conduit 104 and bore 40) and the auxiliary port 70 is now incommunication with the main port 60 (through passage 88, conduit 92,conduit 98 and bore 38).

Operation (FIG. 3)

Assume that the device is pumping low pressure fluid from the inlet 18and discharging it as high pressure fluid to the outlet 20. As describedabove, this causes the valve member 96 to assume its FIG. 3 position.Assume also that the swash plate 48 is in the position shown in FIG. 1.

When operating under such conditions, as the barrel 32 is rotated, acylinder 34 is moved to communicate with the main port 60 and lowpressure fluid is drawn into said cylinder through the flow passage 36by a suction force created by the piston 42 in that cylinder beingwithdrawn. As the barrel continues to rotate, the cylinder moves intocommunication with the auxiliary port 64 and out of communication withthe main port 60. Since, as was described above, the auxiliary port 64is in communication with the main port 60, and since the one way valve76 allows inflow, additional low pressure fluid is drawn into thecylinder as the piston 42 continues to withdraw while the cylinder makesits transit across auxiliary port 64. When the cylinder reaches top deadcenter (TDC), the piston 42 is completely withdrawn and the cylinder issubstantially filled with low pressure fluid.

As the cylinder 34 passes top dead center (TDC) and starts its transitacross auxiliary port 68, the piston 4-2 starts to move into thecylinder to compress the fluid contained therein. The fluid willcontinue to be compressed until it reaches the high pressure present atthe main port 62. When the pressure in the cylinder starts to exceed themain port high pressure, the fluid pressure will open the outflow checkvalve 86 and fluid will flow from the auxiliary port 68 to the main port62. When the cylinder 34 finally moves out of communication with theauxiliary port 68 and into communication with the main port 62, thepressure of the fluid in the cylinder 34 is substantially the same asthe pressure of the fluid at the main port 62, so no shock noise occurs.

The cylinder 34 has so far moved from the main port 60 to the main port62. The return trip from the main port 62 back to the main port 60becomes obvious in view of the above description. Briefly stated, whenthe cylinder 34 moves across the auxiliary port 70, the high pressurefluidcontinues to flow back past the one way valve 90 to the main port62 as the piston 42 continues to move into the cylinder. At bottom deadcenter (BDC), the piston 42 is substantially all the way into thecylinder. As the cylinder moves past bottom dead center and across theauxiliary port 66, the residual fluid in the piston expands and itspressure is reduced until low pressure fluid from the main port 60 isdrawn past the one way valve 82 and into the auxiliary port 66 as thepiston 42 creates a suction as it withdraws from the cylinder 34. Whenthe cylinder moves out of communication with the auxiliary port 66 andinto communication with the main port 60, the pressure of the fluid inthe cylinder 34 is substantially the same as the pressure of the fluidin the main port 60, so no shock noise occurs. The cylinder has thuscompleted a 360 degree transit around the valve plate without anyappreciable shock noise occurring.

When the pressures are reversed, so the machine is motoring oroverhauling, the outlet 20 becomes the low pressure end and the inlet 18becomes the high pressure end. Thus, high pressure fluid enters at themain port 60 and leaves at the main port 62 as low pressure fluid.

This change in pressures causes the shuttle valve member 96 to shift tothe right, as shown in FIG. 3A. The machine will now operate withoutshock noise as described above while delivering fluid in the samedirection.

If this pump is to be used for reversible flow, a reversing valve isrequired in the hydraulic main ports 18 and 20. A reversing valve 300 isshown interconnected to the ports 18 and 20 by means of conduits 302 and304 respectively. The valve 300 is comprised of a multiported valve body306 having a three spool valve member 308 slidable therein toalternately connect the load to either the inlet 18 or the outlet 20.Movement of the valve member 308 is controlled by a cam means 310 whichconnects to the valve member 308 by means of a control rod 312.

The cam means 310 includes a lower portion for controlling movement ofthe valve member 308 and an upper portion for controlling movement ofthe swash plate 48. The lower portion is comprised of an lower surface314 and an upper surface 315. When the control rod 312 bears upon theupper surface 316, the valve member 308 is moved to the left, asillustrated in FIG. 3. If the cam were moved so the control rod 314 boreupon the lower surface 314, the valve member 308 would shift to theright.

The upper portion of the cam means 310 consists of two sloped planarsurfaces 318 and 320 which form an obtuse angle having a vertex at apoint-322. A control rod 324 rides along the surfaces 318 and 320 andhas its other end linked to the control shaft 50 of the swash plate 48.Thus the stroke of the pump is controlled by movement of the cam means300 so that the stroke is reduced from full stroke at the upper end of318 to zero at 322 and then back to full stroke again at the lower endof 320. When the stroke passes through zero (at midpoint 322), the lowerportion of the cam means 300 shifts to reversing valve member 308 toreverse the flow delivered by the pump. Thus, as the stroke is raisedagain in the same direction, delivery of fluid to the load is increasedin the reverse direction.

When the reversing valve 300 is in its neutral position, the valvemember 308 blocks the piping to the load,

7 Jut provides a small by pass or crossfiow between the ports for theconduits 302 and SM to permit a small ielivery of fluid from the pump tocirculate through the valve plate without a build-up of pressure in thepump.

Referring now to FIG. 4, a modified form of the invention is shown,wherein a valve plate 122 is shown having elongated main ports 124 and126 and auxiliary ports 128, 131 132 and 134, said main and auxiliaryports being equiradially spaced from the longitudinal axis of the shaft24. A passage or bore 136 connects the main port 124 to the inlet 18 anda passage or bore 138 connects the main port 126 to the outlet 26).

Each auxiliary port is provided with two valve controlled. passages, oneof which allows inflow to the auxiliary port and-the other of whichallows outflow from it. Each of the passages connects to a conduct whichin turn connects to a flow reversing valve assembly 140.

The auxiliary port 128 is provided with a passage 142 having a one wayvalve 144 therein which allows only inflow to said port, and is alsoprovided with a passage 146 having a one way valve 148 therein whichallows only outflow from said port. The passages 142 and 146 connectrespectively to conduits 151) and 152 which lead to the flow reversingvalve assembly 140.

The auxiliary port 1311 is provided with a passage 154 having a one wayvalve 156 therein which allows only inflow to said port, and is alsoprovided with a passage 158 having a one way valve 160 therein whichallows only outflow from said port. The passages 154 and 158 con nectrespectively to conduits 162 and 164 which lead to the flow reversingvalve assembly 141).

The auxiliary port 134 is provided with a passage 166 having a one wayvalve 16% therein which allows only inflow to said port, and is alsoprovided with a passage 179 having a one way valve 172 therein whichallows only outflow from said port. The passages 166 and 1170 connectrespectively to conduits 174 and 176 which lead to the flow reversingvalve assembly 140.

The auxiliary port 132 is provided with a passage 17% having a one wayvalve 180 therein which allows only inflow to said port, and is alsoprovided with a passage 182 having a one way valve 184 therein whichallows only outflow from said port. The pasages 178 and 182 connectrespectively to conduits 186 and 188 which lead to the flow reversingvalve assembly 140.

The fiow reversing valve assembly 140 is comprised of a multi-portedvalve body 122 and a five spool valve member 194 slidable therein. Thevalve body 192 has eight equally spaced ports in both its upper andlower portions, said ports being arranged so the upper ports aligndirectly over the lower ports. Reading from left to right in FIG. 4, thefirst lower port connects with the conduit the second with the conduit152, the third with the conduit 162, the fourth with the conduit 164,the fifth with the conduit 176, the sixth with the conduit 174, theseventh with the conduit 18% and the eighth with the conduit 186.

Again reading from left to right in FIG. 4, the first upper portconnects with a line or conduit 196, the second with a conduit 198, thethird with a conduit 2%, the fourth with a conduit 2112, the fifth witha conduit 2&4, the sixth with a conduit 206, the seventh with a conduit268 and the eighth with a conduit 216. Since the first upper port alignswith the first lower port, the conduit 1% aligns with the conduit 150.Similarly, the'conduit 198 aligns with the conduit 152, and so on.

The valve member 194 is movable within the valve body 192 to a righthand position (as shown in FIG. 4) where the second, fourth, sixth andeighth ports are open, or to a left hand position where the first,third, fifth and seventh ports are opened. Movement of the valve member194 is controlled by a bi-directional control valve means 212 which inturn is controlled by a cam means 214.

The bi-directional control valve means 212 is comprised of a portedvalve body 216 and a three spool valve memher 213 slidable within saidbody. The valve means 212 is connected to the valve assembly 146 by twoconduits 22d and 222 which extend from ports on the top of the valvebody 216 to ports in the opposite ends of the valve body 122. At thelower portion of the valve body 216, three ports are provided to connectthe conduits 226i and 222, through the valve means 212 to a sump orreservoir 224 which contains a fluid of suitable characteristic foroperating or moving the valve member 194. A line or conduit 226, havinga pump 223 therein, leads from the sump 224 to one of the ports in thelower portion of the valve body 216, and a branch line 230 of theconduit leads to another port in the lower portion of the valve body216. Another conduit 232 leads from the lower portion of the valve body216 to the sump 224.

The valve member 218 is alternately and selectively movable to connectthe sump 224 with the conduits 222 which in turn carry fluid to thevalve assembly 146 to move the valve member 194 to compensate for thedirection of flow. For example, the valve member 218 is shown in theposition which will accommodate flow from right to left, as seen in FIG.4. The pump 228 pumps fluid from the sump 224 through the conduit 226,the branch line 23% and the conduit 22%) and into the valve body 15 2.This fluid causes the valve member 194 to shift to the right, thusopening the second, fourth, sixth and eighth ports in the valve body192. Any excess fluid which was contained on the right side of the valvebody 192 is forced out by the valve member 194, and it flows through theconduit 222, through the valve body 216 and through the conduit 232 intothe sump 224.

If it is desired to have flow from left to right, the valve member 218is moved to the right. The pump 228 then pumps fluid from the sump 224through the conduit 226 and the conduit 222 into the valve body 192,where it will force the valve member 194 to move to the left, thusexposing or opening the first, third, fifth, and seventh ports in thevalve body 192.

A control rod 234 extends between the valve member 218 and the cam means214 for the purpose of controlling movement of said valve member. Thecam means 214 includes a lower portion for controlling movement of thevalve member 213 and an upper portion for controlling movement of theswash plate 48.

The lower portion of the cam means 214 is comprised of atn upper surface236 and a lower surface 238. When the control rod 234 bears upon theupper surface 236, the valve member 218 is moved to the left, asillustrated in FIG. 4. If the cam were moved to the control rod 234 boreupon the lower surface 238, the valve'member 218 would shift to theright.

The upper portion of the cam means 214 consists of a sloped planarsurface 24%. A control rod 246 rides along the surface 249 and has itsother end linked to the control shaft 519 of the swash plate 48. Thus,it can be seen that as the cam means 214 moves, the inclination of theswash plate is changed from full stroke inclination (at the highestpoint of surfaces 240) to no inclination (at mid point 244), to fullstroke inclination in the opposite direction (at the lower point ofsurface 241?). When the control rod 246 is at the point 244, the controlrod 234 is midway between the surfaces 236 and 238, thus causing thevalve member 218 to assume the neutral center position.

The conduits which lead from the upper ports of the valve body 192 ofthe valve assembly are connected to the main ports 124 and 126, eitherdirectly or by passing through an overhauling valve means 248. Theoverhauling valve means comprises a multi-ported valve body 259 having athree spool valve member slidable therein to alternately cover andexpose certain of said ports.

The conduits 196 and 206 merge together to form a single conduit whichconnects into a port on the lower portion of the valve body 250. Theconduits 198 and 264 likewise merge together to form a single conduitwhich connects into a port on the lower portion of the valve body 250.The conduits 200 and 202 merge together to form a single conduit whichconnects into another conduit 254 which in turn connects to the inlet 18(and thus also to the main port 124). The conduits 208 and 210 mergetogether to form a single conduit which connects into another conduit256 which in turn connects to the outlet 20 (and thus also to the mainport 126).

The conduit 254 connects, at its upper end, into a port on the upperportion of the valve body 250. A branch line 258 extends from theconduit 254 into another port on the upper portion of the valve body250. The conduit 256 connects, at its upper end, into a port on theupper portion of the valve body 250, said port being located between theports which connect to the conduit 254 and the line 258.

A branch line 260 extends from the conduit 254 into a port on the leftend of the valve body 250. A branch line 262 extends from the conduit256 into a port on the right end of the valve body 250. Fluid flowthrough these branch lines 260 and 262 determines the position of theoverhauling valve member 252. If high pressure exists at the outlet 20and low pressure exists at the inlet 18, the fluid pressure in thebranch line 262 will exceed that in the branch line 260, thus causingthe valve member 252 to shift to the left. If conditions are reversed,so the inlet is at high pressure and the outlet is at low pressure, thevalve member 252 will shift to the right, as shown.

Operation (FIG. 4)

Valve Member Position Operation Flow Direction Valve Valve Valve PumpingRight to Left- Right Right Left.

Do Left to Right Left eft Right.

Overhauling Right to Left, do Right Left.

Do Left to Right Right Leit Right.

As can be seen by comparing the table and the drawing, FIG. 4illustrates the first condition in the table; that is, pumping with aflow from right to left.

Under such conditions, as a cylinder 34 rotates into communication withthe main port 126, fluid at low pressure is drawn into that cylinder asthe piston 42 within that cylinder withdraws. As the cylinder moves outof communication with the main port 126 and into communication with theauxiliary port 134, the outflow passage 170 is closed and the inflowpassage 166 connects to the main port 126. Fluid continues to be drawninto the cylinder. At bottom dead center (BDC), the piston 42 isfurthest withdrawn from the cylinder 34.

As the cylinder moves into communication with the auxiliary port 130 andthe piston 42 starts to move back into the cylinder, it compresses thefluid contained therein and raises its pressure. When the pressure israised to the pressure of the outlet port 124, fluid flows through theoutflow passage to main port 124. Thus, as the cylinder moves intocommunication with the main port 124, the pressure in the cylinder issubstantially the same as that in the main port, so no shock noiseoccurs.

As the cylinder rotates past the main port 124 and into communicationwith the auxiliary port 128, high pressure fluid from the cylindercontinues to enter the main port 124 th ough the outflow passage 146. Attop dead center (TDC), the piston 42 is furthest into the cylinder, andthe fluid in the cylinder is at high pressure at least equal to that inthe main port 124.

As the cylinder moves past top dead center and into communication withthe auxiliary port 132, the piston 42 starts to Withdraw from thecylinder, thus lowering the fluid pressure in the cylinder by allowingsuch fluid to expand. When the pressure has lowered to the pressure ofthe main port 126, fluid will be drawn into the cylinder from the mainport through the inlet passage 178. When the cylinder finally rotatesback into communication with the main port 126, the pressure in thecylinder is substantially the same as the pressure in the main port, sono shock noise occurs. At this point, the cylinder will have completed a360 degree, substantially silent transit.

In light of the above description of operation, the operation of themachine for the other conditions listed in the above table becomesobvious. It can thus be seen that the present invention provides asilent fluid transfer device which can be used for pumping fluid fromlow pressure to high pressure in either direction (i.e. either left toright or right to left) and which can also be used for overhauling ormotoring fluid from high pressure to low pressure in either direction.

It will be understood that various changes in the details, materials,steps and arrangements of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

What is claimed is: 1. In a hydraulic power transmission machine of thetype having an inlet, an outlet, a rotatable barrel with a plurality ofequally spaced cylinders arranged parallel to the axis of rotation ofsaid barrel, a plurality of pistons located one within each cylinder,and adjustable cam means to move said pistons axially along axis ofrotation as said barrel is rotated, that improvement for permittingsilent flow between said cylinders and said inlet and outlet, whichcomprises in combination with said machine:

a valve plate having a plurality of apertures and a plurality of valvecontrolled passages therein; and

an overhauling valve means including a movable valve member, theposition of which is determined by the pressure differential existingbetween said inlet and outlet;

said valve plate apertures also comprising a pair of spaced opposedelongated main ports and two pairs of spaced opposed auxiliary ports,each of said auxiliary ports communicating with a pair of valvecontrolled passages, the pair being comprised of one passage having aninflow valve and of one passage having an outflow valve;

each of said four pair of passages being connected to a flow reversingvalve means which alternately closes one of the passages of each pairand opens the other of said passages, the direction of fluid flow withinsaid machine determining which passage of each pair will be open andwhich will be closed, the passages being arranged so that the openpassages will always comprise two outflow passages and two inflowpassages, and thus the closed passages will always comprise the same,one of said passages connecting its associated auxiliary port to one ofsaid main ports, another of said passages connecting its associatedauxiliary port to the other of said main ports, the other two auxiliaryports being connected by said passages to said overhauling valve meanswhich alternately connects such associated auxiliary ports to one or theother or" said main ports depending upon the position of said movablevalve member, which in turn depends upon whether the machine isoperating as a pump or as a fluid motor;

two of said auxiliary ports having valve controlled passages which allowonly inflow to their associated auxiliary ports and the other two ofsaid auxiliary ports having valve controlled passages which allow onlyoutflow from their associated auxiliary ports, said passages being soconnected that one inflow and one outflow passage connect to saidoverhauling valve means, and one inflow and one outflow passage connectto said main ports.

2. A machine as defined in claim 1 wherein the passages which are openedby said flow reversing valve are arranged so that one open inflowpassage connects its associated auxiliary port to a main port and oneopen outflow passage connects its associated auxiliary port to the othermain port, the other open inflow passage and the other open outflowpassage connecting their associated auxiliary ports to an overhaulingvalve which alternately connects such associated auxiliary ports to oneor the other of the main ports depending upon whether the machine isoperating as a fluid motor.

3. A machine as defined in claim 1 wherein movement of said flowreversing Valve is controlled by a bidirectional control valve meanswhich in turn is controlled by a movable cam means, said bi-directionalcontrol valve means being movable by said cam means to selectively admitpressurized fluid to either the sinistral or dextral end of said flowreversing valve means, said pressurized fluid thereby causing said flowreversing valve means to shift to a position at the end opposite to thatend at which said pressurized fluid enters.

4. A machine as defined in claim 3 wherein said movable cam meanscomprises two cam portions, one of which controls the position of saidbi-directional control valve means and the other of which controls theposition of said variable cam means.

References Cited by the Examiner UNITED STATES PATENTS 2,288,768 7/42Zimmermann 103-162 2,553,655 5/51 Herman et al. 103162 2,963,983 12/60'Wiggermann l03162 FOREIGN PATENTS 1,020,525 12/57 Germany.

LAURENCE V. EFNER, Primary Examiner.

1. IN A HYDRAULIC POWER TRANSMISSION MACHINE OF THE TYPE HAVING ANINLET, AN OUTLET, A ROTATABLE BARREL WITH A PLURALITY OF EQUALLY SPACEDCYLINDERS ARRANGED PARALLEL TO THE AXIS OF ROTATION OF SAID BARREL, APLURALITY OF PISTONS LOCATED ONE WITHIN EACH CYLINDERS, AND ADJUSTABLECAM MEANS TO MOVE SAID PISTONS AXIALLY ALONG AXIS OF ROTATION AS SAIDBARREL IS ROTATED, THAT IMPROVEMENT FOR PERMITTING SILENT FLOW BETWEENSAID CYLINDERS AND SAID INLET AND OUTLET, WHICH COMPRISES INNCOMBINATION WITH SAID MACHINE: A VALVE PLATE HAVING A PLURALITY OFAPERTURES AND A PLURALITY OF VALVE CONTROLLED PASSAGES THEREIN; AND ANOVERHAULING VALVE MEANS INCLUDING A MOVABLE VALVE MEMBER, THE POSITIONOF WHICH IS DETERMINED BY THE PRESSURE DIFFERENTIAL EXISTING BETWEENSAID INLET AND OUTLET; SAID VALVE PLATE APERTURES ALSO COMPRISING A PAIROF SPACED OPPOSED ELONGATED MAIN PORTS AND TWO PAIRS OF SPACED OPPOSEDAUXILIARY PORTS, EACH OF SAID AUXILIARY PORTS COMMUNICATING WITH A PAIROF VALVE CONTROLLED PASSAGES, THE PAIR BEING COMPRISED OF ONE PASSAGEHAVING AN INFLOW VALVE AND OF ONE PASSAGE HAVING AN OUTFLOW VALVE; EACHOF SAID FOUR PAIR OF PASSAGES BEING CONNECTED TO A FLOW REVERSING VALVEMEANS WHICH ALTERNATELY CLOSES ONE OF THE PASSAGES OF EACH PAIR ANDOPENS THE OTHER OF SAID PASSAGES, THE DIRECTION OF FLUID FLOW WITHINSAID MACHINE DETERMINING WHICH PASSAGE OF EACH PAIR WILL BE OPEN ANDWHICH WILL BE CLOSED, THE PASSAGES BEING ARRANGED SO THAT THE OPENPASSAGES WILL ALWAYS COMPRISE TWO OUTFLOW PASSAGES AND TWO IN FLOWPASSAGES, AND THUS THE CLOSED PASSAGES WILL ALWAYS COMPRISE THE SAME,ONE OF SAID PASSAGES CONNECTING ITS ASSOCIATED AUXILIARY PORT TO ONE OFSAID MAIN PORTS, ANOTHER OF SAID PASSAGES CONNECTING ITS ASSOCIATEDAUXILIARY PORT TO THE OTHER OF SAID MAIN PORTS, THE OTHER TWO AUXILIARYPORTTS BEING CONNECTED BY SAID PASSAGES TO SAID OVERHAULING VALVE MEANSWHICH ALTERNATELY CONNECTS SUCH ASSOCIATED AUXILIARY PORTS TO ONE OR THEOTHER OF SAID MAIN PORTS DEPENDING UPON THE POSITION OF SAID MOVABLEVALVE MEMBER, WHICH IN TURN DEPENDS UPON WHETHER THE MACHINE ISOPERATING AS A PUMP OR AS A FLUID MOTOR; TWO OF SAID AUXILIARY PORTSHAVING VALVE CONTROLLED PASSAGES WHICH ALLOW ONLY INFLOW TO THEIRASSOCIATED AUXILIARY PORTS AND THE OTHER TWO OF SAID AUXILIARY PORTSHAVING VALVE CONTROLLED PASSAGES WHICH ALLOW ONLY OUTFLOW FROM THEIRASSOCIATED AUXILIARY PORTS, SAID PASSAGES BEING SO CONNECTED THAT ONEINFLOW AND ONE OUTFLOW PASSAGE CONNECT TO SAID OVERHAULING VALVE MEANS,AND ONE INFLOW AND ONE OUTFLOW PASSAGE CONNECT TO SAID MAIN PORTS.